An ion-beam etching apparatus has heretofore been composed of three systems, an ion beam system including an ion source and a beam focusing section, an ion etching system including a beam scanner and a specimen chamber, and a vacuum exhaust system.
Generally, in a conventional ion beam processing system, 3 - 10 kV is applied on an ion coming from the ion source by means of an electrical lens; the ion is then drawn out, and thereafter, by means of the focusing lenses, the ion beam diameter and its profile are changed at the surface of a specimen.
FIG. 1 is a constructional diagram of a conventional ion beam etching apparatus, in which numeral 1 designates an argon gas entrance; 2, a thermal cathode; 3, the ion source section; 4, an anode; 5, a drawing-out electrode; 6, a focusing electrodes; 7, the beam focusing section for focusing the beam; 8, the ion beam system; 9, a variable slit; 10, the scanning electrodes; 11, vacuum exhaust system (A); 12, a gate valve; 13, the specimen chamber; 14, the specimen; (15), the specimen table; 16, vacuum system (B); 17, the ion etching system; and 18, the vacuum exhaust system.
Those are two methods of irradiating the ion beams onto the specimen surface, that is (1) irradiating the specimen with the ion beams uniformly spread and (2) scanning and irradiation with fine ion beams. The former method is used in etching a wide surface of the sample by spread ion beams, and the latter in ion beam milling. It is by this latter method that a wide flat surface may be obtained by way of etching while scanning with the ion beams.
The characteristics of the ion beam processing methods include: (a) very slight contamination by the residual gas because the operation is performed under a high degree of vacuum; (b) control of the angle of irradiation and the ion current; (c) a high-resolution pattern without side etching; and (d) a low etching rate.
In the fine processing technique employed in manufacturing electronic high density components, the surface or film etching techniques are important. Especially, techniques enabling the etching to be performed at low processing rates are necessary. If the conventional ion beam etching system is utilized for this purpose, the current density of the ion beam needs to be decreased. As the current density is decreased, the adsorption of the residual gas by the specimen increases; on extreme occasions, the effect is an increase in the amount of the residual gas adsorbed, rather than meeting the requirement for etching the surface of the workpiece. Moreover, high degrees of vacuum in the system are required. Since a conventional system is not supplied with a second ion monitor, it is not possible to check on the changes in the intensity of the secondary ion or the type of the secondary ion which is produced in concert with the etching. For this reason, the exact etching depth and the amount of the material left to be etched can not be determined.